The present invention generally relates to a method of pressure processing enclosures having bi-stable valves. More specifically, the present invention relates to a method of pressurizing or depressurizing enclosures singly, or preferably en masse, where each enclosure comprises a bi-stable valve having open and closed modes, wherein a sudden change of external pressure causes the valves to close, generally irreversibly.
Writing instruments such as pens are commonly provided with a cartridge or a refill such that, when the ink within the pen or refill is fully depleted, only the refill requires replacement. As a result, a variety of decorative pen housings can be provided to receive a standard refill so that the housing can be used repeatedly, requiring replacement of the refill only.
Refills may be pressurized, whereby a smooth and continuous flow of ink is produced regardless of the orientation of the pen itself. For a disposable product, it is preferable that the refill be supplied to the end user pressurized, without subsequent repressurization being necessary.
Pressurization may be achieved by providing chemicals within the refill that react over time, creating gas reaction products that maintain the pressure of the sealed refill tube. This is relatively complicated, expensive and imprecise.
Another method of pressurizing a refill involves pushing a stopper into the open proximal end of the ink tube, whereby the air between the end of the ink column and the stopper is compressed. With this method, the amount of ink that may be loaded into the ink tube is limited, because a portion of the volume, which is needed to compress the column of air, is lost as storage space for the ink.
Yet another method of introducing gas into a refill employs a valve pressed into the proximal end of the ink tube. For example, in the minimal configuration the valve employs one seal (U.S. Pat. No. 4,587,999 to Boiko, et al.), or three or more in a more complex configuration (U.S. Pat. No. 5,738,459 to Smith). Such valves necessarily must have low sealing forces, as the small size of the valve limits the size of springs or other elements employed to close the valve. Imperfections or contaminants on the sealing surfaces may thereby result in loss of pressurization.
A need, therefore, exists for an inexpensive and reliable valve capable of generating high sealing forces that also provides for self-actuated closure.
The present invention provides an initially open valve assembly having an inlet (proximal end) and an outlet (distal end) and a bi-stable element therebetween that closes the valve upon sudden reduction of inlet pressure. In a preferred embodiment, the valve assembly is used in a pen refill. In a second embodiment, the valve is used in a reversed orientation, so that a sudden increase of inlet pressure closes the valve.
The bi-stable element has an open mode, whereby fluid, particularly gaseous fluid, is allowed to flow therethrough, and a closed mode wherein fluid flow therethrough is blocked. The bi-stable element is preferably a curved disk molded in the closed mode shape from an elastomeric or polymeric material. The disk may also comprise a thin metallic layer or foil to prevent gaseous diffusion therethrough. The valve assembly may be pressed into the proximal end of the tubular ink reservoir of a refill (or other enclosure), with the valve in the initially open mode. Once the enclosure is pressurized, inlet pressure may be rapidly reduced, causing the disk to become unstable and invert. The force generated by the inversion of the disk is used to assist the closure of the valve. If the inlet pressure is reduced at a rate less than that required for inversion of the disk, pressure within the enclosure drops. External pressure may therefore be reduced slowly to scavenge the initial gases present within the reservoir, e.g. oxygen. One or more pressure cycles may be used.
If the valve orientation is reversed, the external pressure may be first dropped, allowing the enclosure to at least partially evacuate, and then rapidly increased to actuate the valve, thereby resulting in a rigid enclosure that contains a lower than atmospheric pressure, or a flexible enclosure having reduced free-space (with or without reduced internal pressure in the final configuration) due to compression of enclosure walls by the atmosphere. Such a flexible enclosure may be used to contain oxygen sensitive materials such as seeds, coffee, or alternatively may be used to minimize packing volume. Likewise, rigid enclosures may be evacuated for storage of foodstuffs or other materials.
For use with an enclosure such as an ink pen cartridge or refill, the valve assembly comprises at least one distal port and at least one proximal port. An inner support serves to enhance the sealing of an annular ring seal against the inner surface of ink reservoir, to carry the at least one proximal (inlet) port, and, optionally, a sealing plug or other element for sealing the at least one distal port. (The terms distal and proximal are interchanged for the reversed orientation of the valve.) The bi-stable element comprises means for closing the valve, and generally also comprises at least one distal (outlet) port allowing fluid communication with the body of the refill enclosure. The bi-stable element preferably comprises a curved disk, which may have varying thickness, and which may optionally have a thickened central area (boss) for enhancing the sealing of a proximal port penetrating the disk at that point. The disk may optionally carry a plug or other means for sealing the proximal port. The periphery of the disk, forming a continuous seal to the annular ring, is preferably reduced in thickness to allow for inversion of the disk. It is preferred that, given a flow rate, the pressure drop across the proximal port is greater than that across the distal port, so that the bi-stable element may be quickly actuated with minimal loss of enclosure pressure.
In general, in the preferred inventive method, one or more enclosures having open valves are placed into a chamber providing an external gaseous environment to the enclosures at a first pressure. The pressure within the chamber is then changed to a second pressure different from the first pressure, with the pressure within the enclosures tending to approach this second pressure. The chamber pressure is then changed to a third pressure different from the second pressure at a rate sufficient to close the valves, and the enclosures are then removed from the chamber. Prior to closure, the chamber may be pressurized (cycled) to other pressures between the first and second and/or second and third pressures, at a rate insufficient to close the valves.
It is an object of the present invention, therefore, to provide method of pressurizing a plurality of enclosures having bi-stable valve elements.
It is an object of at least one embodiment of the present invention to provide a method of pressurizing a plurality of enclosures having bi-stable valve elements, whereby gas initially present within the enclosure may be scavenged by cycling the pressure external to the enclosure.
It is another object of at least one embodiment of the invention to provide a method of pressurizing ink pens, whereby a bi-stable valve is automatically closed upon the reduction of pressure external to the pens.
It is an object of at least one embodiment of the present invention to provide a method of processing a plurality of enclosures having bi-stable valves, whereby the final pressure therein is less than atmospheric.
It is an object of at least one embodiment of the present invention to provide a method of processing a plurality of flexible enclosures having bi-stable valves, whereby the free volumes of the enclosures are reduced.